Hydrocarbon charge history of the Paleogene reservoir in the northern Dongpu Depression,Bohai Bay Basin,China

The hydrocarbon charge history of the Paleogene in the northern Dongpu Depression was analyzed in detail based on a comprehensive analysis of the generation and expulsion history of the major hydrocarbon source rocks, fluorescence microscopic features and fluid inclusion petrography. There were two main stages of hydrocarbon generation and expulsion of oil from the major hydrocarbon source rocks. The first stage was the main hydrocarbon expulsion stage. The fluorescence microscopic features also indicated two stages of hydrocarbon accumulation. Carbonaceous bitumen, asphaltene bitumen and colloidal bitumen reflected an early hydrocarbon charge, whereas the oil bitumen reflected a second hydrocarbon charge. Hydrocarbon inclusions also indicate two distinct charges according to the diagenetic evolution sequence, inclusion petrography features combined with the homogenization temperature and reservoir burial history analysis. According to these comprehensive analysis results, the hydrocarbon charge history of the Paleogene reservoir in the northern Dongpu Depression was divided into two phases. The first phase was from the late Dongying depositional period of the Oligocene to the early uplift stages of the late Paleogene. The second phase was from the late Minghuazhen period of the Pliocene to the Quaternary. Reservoirs formed during the first period were widely distributed covering the entire area. In contrast,reservoirs formed during the second period were mainly distributed near the hydrocarbon generation sags. Vertically, it was characterized by a single phase in the upper layers and two phases in the lower layers of the Paleogene.

Turbidite Reservoirs in the Dongying Sag,Bohai Bay Basin:Interactions between Carbonate Cementation and Hydrocarbon Charge

Turbidite sandstones have become increasingly significant in hydrocarbon exploration.Carbonate cementation occur commonly in turbidite reservoirs developing within the Paleocene lacustrine basins,Northeastern China.This study utilizes core data,thin section data and production data to investigate the interaction between the carbonate cementation and hydrocarbon charge within turbidite reservoirs in the Niuzhuang Sub-sag of the Dongying Sag,Bohai Bay Basin,East China.The results reveal that the carbonate cementation is mainly developed at the top and bottom of the turbidite sandbodies,and even forms carbonate cement shells.Three stages of hydrocarbon accumulation are identified based on fluid inclusion analysis:stage I(27.5–24.6 Ma),stage II(14.0–5.0 Ma),and stage III(5.0–0 Ma).The interaction between the carbonate cementation and hydrocarbon charge has significant controls on the formation of a turbidite reservoir.The temporal relations and intensity relations between the two factors should be considered significantly.Moreover,hydrocarbon charge during the early stage can inhibit the carbonate cementation,favoring the hydrocarbon accumulation in turbidite reservoirs.Many deep-lacustrine turbidite sandbodies surrounded by source rocks with abnormal high pressure,are also favorable for hydrocarbon accumulation.These results suggest that some deeply buried turbidite sandbodies with similar geological settings have high potential for hydrocarbon exploration.

K-Ar Dating of Authigenic Illites and Its Applications to the Study of Hydrocarbon Charging Histories of Typical Sandstone Reservoirs in Tarim Basin, China

The Tarim Basin in China comprises eight sets of sandstone reservoirs, five of which are investigated in detail in this study. The main purpose of this study is to investigate the hydrocarbon charging histories of reservoirs by applying K-Ar dating of authigenic illites. The ages of authigenic illites from the Lower Silurian bituminous sandstones in the Central Uplift area range from 383.5 to 235.2 Ma, suggesting that the Silurian oil accumulations were formed from the late Caledonian till the late Hercynian. The ages of authigenic illites from the Upper Devonian Donghe Sandstone reservoirs range from 263.8 to 231.3 Ma, indicating that hydrocarbon accumulations within the Donghe sandstone were formed mainly in the late Hercynian. The authigenic illites ages from the Lower Jurassic Yangxia Group sandstones in the Yinan-2 gas reservoir (Yinan-2, Kuqa Depression) range from 28.1 to 23.9 Ma, suggesting that the initial hydrocarbon charging occurred in the Miocene. The ages of the authigenic illites from the Lower Cretaceous sandstones in the Akemomu gas field (Ake-1, Kashi Sag, Southwest Depression) range from 22.6 to 18.8 Ma, indicating a probable early oil accumulation or early migration of hydrocarbon within this area. The illites from the Paleogene sandstones in the Dina-2 gas reservoir (Dina-201, Kuqa Depression) have a detrital origin; they cannot be used to study the hydrocarbon charging histories. The ages of authigenic illites in the underlying Cretaceous sandstones in the same well (Dina-201) range from 25.5 to 15.5 Ma, indicating that hydrocarbon charging in this reservoir probably occurred within the Miocene. This study highlights the potential of applying K-Ar dating of authigenic illites to investigate the timing of hydrocarbon charging histories of the Tarim Basin reservoir sandstones.

Determination of Hydrocarbon Charging History by Diagenetic Sequence and Fluid Inclusions:A Case Study of the Kongquehe Area in the Tarim Basin

Petrographic analysis of hydrocarbon inclusions in reservoirs is the basis and prerequisite for study of hydrocarbon charge history using fluid inclusion analysis.Samples from Silurian reservoirs in the Kongquehe area were studied with microscopy,cathode luminescence and scanning electron microscopy,and the paragenetic sequence of diagenetic events was established.Aqueous and oil inclusions were found in four different occurrences,i.e.,① in healed cracks in detrital quartz grains,② in quartz overgrowths that were formed relatively early in diagenesis,③ in healed cracks crosscutting quartz overgrowths and detrital quartz,and ④ in paragenetically late calcite cements.Solid bitumens were found in intergranular pores and in late fractures,whereas gas inclusions occur in healed cracks crosscutting quartz overgrowths and detrital quartz.The homogenization temperatures of aqueous（Th_（aq）） and oil incluisons（Th_0） within individual fluid inclusion assemblages are very consistent,suggesting that the microthermometric data are reliable.The Th_（aq） values are generally larger than Th_0,indicating the oil charging events took place at significant depths.The results suggest that there were at least two episodes of hydrocarbon charging in the Kongquehe area：the early hydrocarbon charging occurred in late Caledonian,dominated by oil,and the late hydrocarbon charging occurred in the Yanshan-Himalayan,first by oil and then gases.In addition,two episodes of hydrocarbon reservoir adjustment and destruction occurred in the Hercynian and Himalayan,respectively,forming solid bitumen.

Evolution of Diagenetic Fluid of the Dawsonite-Bearing Sandstone in the Jiyang Depression,Eastern China

Based on the petrology,isotope geochemistry and fluid inclusions analysis,we established the evolutionary mode of the diagenetic fluid of dawsonite-bearing sandstone in the Jiyang Depression.Dawsonite-bearing sandstone is characterized by double injection of CO_(2)and oil-gas in the Jiyang Depression that have experienced a relatively complex diagenetic fluid evolution process.The diagenetic sequence of secondary minerals involves secondary enlargement of quartz,kaolinite,first-stage calcite,dawsonite,second-stage calcite,ferrocalcite,dolomite and ankerite.Hydrocarbon charging in the dawsonite-bearing sandstone occurred at around 2.6–0 Myr.The CO_(2)charging event occurred during Dongying tectonism,forming the Pingfangwang CO_(2)gas reservoir,which provided an abundant carbon source for dawsonite precipitation.Carbon and oxygen isotopic compositions of dawsonite demonstrate that CO_(2)forming the dawsonite was of an inorganic origin derived from the mantle,and that water mediating the proc-ess during dawsonite precipitation was sequestered brine with a fluid temperature of 82℃.The evolutionary sequence of the diagenetic fluid in the dawsonite-bearing sandstone was:alkaline syngenetic fluids,weak alkaline fluids during organic acid forma-tion,acidic fluids in the early stage of CO_(2)injection,alkaline fluids in the late stage of CO_(2)injection,and weak alkaline fluids during oil and gas charging.The mode indicates an increase in-HCO_(3)because of the CO_(2)injection,and the loss of Ca^(2+)and Mg^(2+)due to the precipitation of carbonate minerals.Therefore,the evolutionary mode of diagenetic fluids is in good agreement with high HCO_(3)^(-),low Ca^(2+)and low Mg^(2+)composition of the present formation water in the dawsonite-bearing sandstone.

Fluid evolution and hydrocarbon accumulation model of ultra-deep gas reservoirs in Permian Qixia Formation of northwest Sichuan Basin,SW China

The fluid evolution and reservoir formation model of the ultra-deep gas reservoirs in the Permian Qixia Formation of the northwestern Sichuan Basin are investigated by using thin section,cathodoluminescence,inclusion temperature and U-Pb isotopic dating,combined with gas source identification plates and reservoir formation evolution profiles established based on burial history,thermal history,reservoir formation history and diagenetic evolution sequence.The fluid evolution of the marine ultra-deep gas reservoirs in the Qixia Formation has undergone two stages of dolomitization and one phase of hydrothermal action,two stages of oil and gas charging and two stages of associated burial dissolution.The diagenetic fluids include ancient seawater,atmospheric freshwater,deep hydrothermal fluid and hydrocarbon fluids.The two stages of hydrocarbon charging happened in the Late Triassic and Late Jurassic–Early Cretaceous respectively,and the Middle to Late Cretaceous is the period when the crude oil cracked massively into gas.The gas reservoirs in deep marine Permian strata of northwest Sichuan feature multiple source rocks,composite transportation,differential accumulation and late finalization.The natural gas in the Permian is mainly cracked gas from Permian marine mixed hydrocarbon source rocks,with cracked gas from crude oil in the deeper Sinian strata in local parts.The scale development of paleo-hydrocarbon reservoirs and the stable and good preservation conditions are the keys to the forming large-scale gas reservoirs.

Hydrocarbon charging histories of the Ordovician reservoir in the Tahe oil field, Tarim Basin, China

The Ordovician reservoir of the Tahe oil field went through many tectonic reconstructions, and was characterized by multiple hydrocarbon chargings. The aim of this study was to unravel the complex charging histories. Systematic analysis of fluid inclusions was employed to complete the investigation. Fluorescence observation of oil inclusions under UV light, and microthermometry of both oil and aqueous inclusions in 105 core samples taken from the Ordovician reservoir indicated that the Ordovician reservoir underwent four oil chargings and a gas charging. The hydrocarbon chargings occurred at the late Hercynian, the Indo-Sinian and Yanshan, the early Himalaya, the middle Himalaya, and the late Himalaya,respectively. The critical hydrocarbon charging time was at the late Hercynian.

Sequence of densification and hydrocarbon charging of Xu2 reservoir in Anyue–Hechuan area,Sichuan Basin,China

The sequence of the densification and hydrocarbon charging of the Xu2 reservoir in the Anyue–Hechuan area of Central Sichuan Basin is discussed.The diagenetic sequence is considered a time line to determine the historical relationship between the densification process and the hydrocarbon charging of the Xu2 reservoir in the study area:Early diagenetic stage B(the first stage of hydrocarbon charging,which was about 200–160 Ma ago,with a porosity of about 20%,consolidated and not tight)→middle diagenetic stage A(the second stage of hydrocarbon charging,which was about 140–120 Ma ago,with a porosity of 10%–20%and relatively tight)→middle diagenetic stage B(the third stage of hydrocarbon charging,which was about 20–5 Ma ago,with a porosity of 6%–10%and tight;However,fractures have developed).The study results prove that large-scale hydrocarbon charging and accumulation completed before the densification of the Xu2 reservoir,showing that the Upper Triassic Xujiahe Fm unconventional tight reservoir in the Sichuan Basin is prospective for exploration.

Coupling relationship between reservoir diagenesis and hydrocarbon accumulation in Lower Cretaceous Yingcheng Formation of Dongling,Changling fault depression,Songliao Basin,Northeast China

The Lower Cretaceous Yingcheng Formation in the southern Songliao Basin is the typical tight oil sandstone in China.In order to better predict the petrophysical properties of the tight sandstone reservoirs in the Lower Cretaceous Yingcheng Formation,Songliao Basin,Northeast China,the diagenesis and porosity evolution was investigated using a suite of petrographic and geochemical techniques including thin section analysis,scanning electron microscopy,mercury intrusion and fluid inclusion analysis,on a set of selected tight sandstone samples.Combined with the histories of burial evolution,organic matter thermal evolution and hydrocarbon charge,the matching relationship between reservoir porosity evolution and hydrocarbon accumulation history is analyzed.The result showed that the tight sandstone reservoirs characterized of being controlled by deposition,predominated by compaction,improved by dissolution and enhanced by cementation.The hydrocarbon accumulation period was investigated using a suite of hydrocarbon generation and expulsion history,microfluorescence determination and temperature measurement technology.According to the homogenization temperature of the inclusions and the history of burial evolution,Yingcheng Formation has mainly two phases hydrocarbon accumulation.The first phase of oil and gas is charged before the reservoir is tightened,the oil and gas generated by Shahezi source rocks enter the sand body of Yingcheng Formation,influenced by the carrying capability of sand conducting layer,oil and gas is mainly conducted by the better properties and higher connectivity sand body and enriched in the east,which belongs to the type of densification after hydrocarbon accumulation.The second phase of oil and gas charge after densification,which belongs to the type of densification before the hydrocarbon accumulation.

Multi-Stage Fluid Charging and Critical Period of Hydrocarbon Accumulation of the Sinian Dengying Formation in Central Sichuan Basin

Objective The natural gas exploration of the Sinian reservoirs in the central Sichuan Basin has made a significant breakthrough in recent years, and has thus attracted much attention among geologists. The Sichuan Basin is known to have complicated geological settings, which has experienced multiple stages of tectonic evolution, fluid charging and hydrocarbon accumulation. This research aims to determine the geochemical characteristics of each stage of fluids, the features and time interval of fluid activity in different geologic periods, and further to restore the critical period and geological age of the hydrocarbon accumulation.

Relationship Between Paleogene Reservoir Densification and Hydrocarbon Accumulation in the Xihu Depression

Fluid inclusion analysis and testing were conducted to clarify the relationship between reservoir densification and hydrocarbon accumulation in the Paleogene Pinghu and Huagang formations in the Xihu Depression.The hydrocarbon accumulation stages of the reservoirs were studied in combination with the reconstruction results of burial and thermal evolution histories.Furthermore,the relationship between reservoir densification and accumulation charging was clarified in combination with the pore evolutionary history.In accordance with the time relation between reservoir densification and hydrocarbon charging,the reservoirs were classified into three types:pre-charging,syn-charging,and after-charging densification.Results indicated that large-scale hydrocarbon charging occurred in 11–0Myr.Reservoir densification was mainly caused by strong mechanical compaction and pore filling by well-developed siliceous and carbonate cements.Entering the middle diagenetic stage A1,the reservoir was under an acidic-diagenetic environment,resulting in the development of secondary dissolution pores.If large-scale hydrocarbon charging occurred during this period,then an after-charging densification reservoir,which is the most suitable type for hydrocarbon accumulation,might have developed.Entering the middle diagenetic stage A2,the reservoir was under an acidic-alkaline transitional diagenetic environment.During this stage,dissolution became weak,and compaction and cementation were enhanced,resulting in the continuous loss of pore space and reservoir densification.Entering the middle diagenetic period B,the reservoir was under an alkaline-diagenetic environment,and the reservoir had been largely densified.If large-scale hydrocarbon charging occurred during this period,a pre-charging densified reservoir,which is the worst reservoir type for hydrocarbon accumulation,might have developed.

Hydrocarbon Charging and Accumulation Process of the Large Bozhong19-6 Condensate Gas Reservoirs in the Southwestern Bozhong Sub-Basin,Bohai Bay Basin,China

The Bozhong19-6(BZ19-6)condensate gas reservoirs,located in the southwestern Bozhong sub-basin,Bohai Bay Basin,China,were paleo-oil reservoirs in the geological past and have undergone at least three successive hydrocarbon charging events.The hydrocarbon migration and accumulation process of“early oil and late gas”has occurred in the current reservoirs.At the end of the sedimentation of the Guantao Formation(N_(1)g,∼12 Ma),the reservoirs began to fill with first stage low-moderate mature crude oil.At the late stage of the Lower Minghuazhen Formation(N_(1)ml)(∼6.7 Ma),the reservoirs were largely charged with second stage high mature crude oil.Since the deposition of the upper Minghuazhen Formation(N_(2)m^(u),∼5.1 Ma),the paleo-oil reservoirs were transformed into shallow Neogene reservoirs due to the reactivation of basement faults.From the late stage of the N_(2)m^(u)to the present day(∼2.8–0 Ma),the reservoirs were rapidly filled by natural gas within a short period.In addition,analysis of the formation of the reservoir bitumen and the conspicuous loss of the lower molecular weight n-alkanes in the crude oil reveal that the injection of a large amount of gas in the late stage caused gas flushing of the early charged oil.

Variation and mechanisms of clastic reservoir quality in the Paleogene Shahejie Formation of the Dongying Sag, Bohai Bay Basin, China

Reservoir quality varies greatly in the Shahejie Formation in the Dongying Sag. It is essential to analyze the variation and mechanisms of reservoir quality for determining the controlling factors based on cores, porosity measurements and fluid inclusion techniques and so on. The sandstones in the fluvial, （fan） delta-front have the best reservoir quality due to the depositional conditions mechanically controlling the petrology configuration and the primary porosity, and chemically influencing the diagenesis and development of secondary pores. The activity of the boundary faults and the sedimentary facies dominate the variation of reservoir quality in different areas and intervals. The reservoir quality varies with the position of sandstone beds in different vertical models of sandstone and mudstone. This mainly arose from the strong cementation or strong dissolution in the sandstone caused by the diagenesis evolution of adjacent mudstone. With higher oil saturation reservoir quality is better because the hydrocarbon charge favors dissolution and restricts cementation. Diagenesis, depositional conditions and tectonic setting are the key controls of reservoir quality in the Shahejie Formation of the Dongying Sag.

Hydrocarbon charging of the Ordovician reservoirs in Tahe-Lunnan area, China

The Tahe-Lunnan hydrocarbon province is China's largest region with oil-and-gas-producing marine carbonate rocks. However, in terms of multi-source hydrocarbon generation, multi-episode reservoir adjustment and reconstruction, it remains unsettled how to determine the geological period of primary hydrocarbon filling of the Ordovician reservoir in this region. Based on the analysis of distribution and properties of reservoir, hydrocarbon filling of the Cambrian source rocks in the Late Caledon stage has largely been destroyed. However, hydrocarbon filling of the Middle Ordovician source rocks in the Early Carboniferous resulted in the major body of crude oil. During the charging process, the hydrocarbons were oxidatively degraded to heavy oil due to the poor closure conditions, which is corroborated by homogenization temperature of inclusions. Moreover, the capturing of hydrocarbon inclusions with high-temperature does not represent the filling of mature petroleum in the later period, but represents the result of the natural gas containing light fraction. Therefore, the Tahe-Lunnan area underwent two hydrocarbon filling processes, and the invasion of excessive dry gas led to a gas-washing fractionation upon the original Ordovician reservoirs.

Bitumen formation of Cambrian Longwangmiao Formation in the central Sichuan and its implication for hydrocarbon accumulation

Based on organic petrology,organic geochemistry and SEM method,type,formation period and source of bitumens in the Cambrian Longwangmiao Formation in the central Sichuan Basin were well investigated,and combined with fluid inclusions and tectonic evolution characteristics,the hydrocarbon accumulation history of the gas reservoir of the Longwangmiao Formation in the Anyue gasfield was also studied.The result shows that all bitumens in the Longwangmiao Formation was from the Lower Cambrian source rocks,it had multiple genetic types which was dominated by the pyrolysis genetic type;the bitumens were formed into three stages,i.e.,the bitumen of the oxidized water-washing type in the first stage,the bitumen of the precipitated type in the second stage,and the bitumen of the pyrolyzed type in the third stage;the gas reservoir in the Anyue gasfield experienced five stages of hydrocarbon charging,including two stages of liquid hydrocarbon charging,charging of the kerogen pyrolysis gas in the Late Triassic-Early Jurassic,charging of the crude oil pyrolysis gas in the Late Jurassic-Early Cretaceous and charging of the dry gas charging in the Himalayan trap reformation and adjustment process.

Diagenetic Sequence and Genetic Mechanism of Silurian Tight Sandstone Reservoirs in the Eastern Tarim Basin, Northwest China

The Silurian stratigraphic sequence has recently become one of the most important exploration targets in the Tarim Basin, with a considerable amount of profitable hydrocarbon pools discovered in the central Tarim Basin. Previous exploration activities indicate that the Silurian stratigraphic sequence in the eastern Tarim Basin has great hydrocarbon exploration potential. The Silurian reservoirs comprise a set of tight marine sandstones, whose diagenetic sequence and genetic mechanism are still poorly understood. The complex relationship of hydrocarbon generation, the timing of the peak expulsion of the source rocks and the evolution of the reservoirs remains unclear. An integrated description and analysis have been carried out on core samples from eleven wells selected from the eastern Tarim Basin. A range of petrographic and geochemical analyses were conducted. By using an integrated approach with thin-section petrography, scanning electron microscopy（SEM）, cathodoluminescence（CL）, carbon and oxygen isotope geochemistry, formation water analysis, X-ray diffractometry（XRD）, electron probe microanalysis and fluid inclusion microthermometry, the genesis and occurrence of individual diagenetic events were documented to reconstruct the diagenetic sequence and diagenetic model for the Silurian sandstone. Additionally, the tight nature of the Silurian reservoirs can mainly be attributed to the compaction processes and cementation. In particular, the destructiveness of the compactional processes to the original porosity is far greater than that from the cementation. Furthermore, fluid inclusion analyses also indicate that the Silurian sandstone has experienced three phases of hydrocarbon charge. The first two phases occurred during the eodiagenesis stage（from the Late Silurian to the Early Devonian and from the Late Carboniferous to the end of the Late Permian）, when the Silurian sandstone was not tight and had a porosity of greater than 20%. The third phase occurred during the stage B of mesodiagenesis（since the Late Cretaceous）, when the Silurian sandstone was fully tight.

Key Elements Controlling Oil Accumulation within the Tight Sandstones

Tight oil sandstone reservoirs with low porosity and permeability, which are an unconventional petroleum resource, have been discovered in the Jurassic intervals of the central Junggar Basin, the northwestern China. To reveal the accumulation mechanism, a relatively comprehensive research was conducted, including oil-source correlation, porosity evolution, and hydrocarbon charging history. The results show that crude oil of these tight sandstone reservoirs were mainly from Permian source rocks with some contribution from Jurassic source rocks. The reservoirs were buried at shallow depth（〈3 100 m） and exposed to weak diagenesis, and thus had high porosity（18.5%） when the Permian-sourced oil from Permian source rock was charging, indicating high GOI values（〉5%）. In contrast, the sandstone reservoir had already become tight and did not provide available space to accumulate oil due to severe compaction and cementation when hydrocarbon from Jurassic source rock filled, evidenced by low GOI values（〈5%）. Therefore, reservoir porosity controls the oil accumulation within tight sandstone. Whether tight sandstone reservoirs accumulate oil depends on the reservoir quality when hydrocarbons charge. Before the exploration of tight oil sandstone reservoirs, it should be required to investigate the relationship between oil charging history and porosity evolution to reduce the exploration risk and figure out the available targets.

Research advances in the formation poredynamics of sedimentary basins

In the 21st century,the geodynamics is developing towards quantitative researches.However,due to the irreversible geological processes,it was very difficult to recover the geological process.In particular,the restoration of geological parameter evolution process at the microscopic scale has become a major scientific problem in geology presently.Thereby,a concept of the formation poredynamics is revised and proposed,and the formation poredynamics is a fundamental discipline which focus on the mechanical characteristic of porous media,the pore evolution law,the dynamic genesis and the seepage property of pore fluid during the burial process of clastic rocks.Moreover,it is a new interdiscipline of underground diagenetic dynamics and pore fluid dynamics,and also is as an important part of sedimentary basin dynamics.Research advances were made in both basic theory and applied research.The advances in the basic theory include:(1)the static equilibrium principle of the formation pore,(2)the porosity evolution mechanism and quantitative model of sandstone during the burial diagenetic process,(3)the compaction characteristic and the porosity evolution quantitative model of mudstone,(4)the theoretical relationship between the underground pore fluid temperature and the pore fluid pressure,(5)the influence of the tectonism-induced additional geostress on the pore fluid pressure,and(6)the relationship between the mudstone compaction and the vitrinite reflectance(R_(o))of organic matter.The advances in the applied research include:(1)the geotemperature-geopressure system division of the sedimentary basin and the interpretation of the hydrocarbon distribution dynamic,(2)the modification of the strata pressure prediction model,(3)the construction of the reservoir critical properties and the reservoir dynamics evaluation system,(4)the simulation of the evolution process of the formation fluid pressure,(5)the numerical simulation and physical experimental simulation on the sandstone hydrocarbon charging dynamics,and(6)the dynamic process analysis of the hydrocarbon accumulation in tight sandstone.Through the integration between the pore genesis evolution and the pore fluid dynamic evolution,the formation poredynamics is one of the representative discipline branches that the geological dynamics research had developed toward the underground microscopic scale in recently 20 years,and it also is an inevitable result from the quantitative development of the formation and distribution mechanisms of sedimentary mineral deposits.Based on the formation poredynamics research,eight important research achievements are summarized,and the geological researches are extended from the macroscopic scale to the microscopic scale,to find out the pore parameter evolution law under control of the formation pore evolution during the burial process,and update and improve exploration and production application technologies.

The geochemical evidences of sulphur oil sources in the BZ35/36 structures of the Huanghekou Sag, Bohai Bay Basin, China

Crude oils in the BZ35/BZ36 fields found within the Paleogene Dongying and Shahejie formations in the Huanghekou Sag of the Bohai Bay Basin,China have generally high density,viscosity,and sulfur content.Their physical properties and geochemical features have obvious differences when compared with crude oils from other structures within the Huanghekou Sag.The comparison and analysis of biomarkers(e.g.,pristine/phytane,gammacerane,C24Te/C26TT,C2920S/(20Sþ20R),C29bb/(bbþaa),etc.)show that sour crude oil from the BZ35/BZ36 fields is similar to the sour oil in the Miaoxi Sag adjacent to the eastern of Huanghekou Sag.Sour,low maturity oils in the Miaoxi Sag have likely migrated southwest,while the sweet,higher maturity oils in the Huanghekou Sag have migrated northeast.Crude oils generated from these two sags have focused in the BZ35/BZ36 structures.The source rock of the sour crude oil was most likely formed in a dry climate and strong reducing saline lake.